The Biostatistics Core will serve as a resource and collaborator for all projects related to this Program Project. In particular, the Biostatistics Core will consult on the statistical design of all projects and will consult on the application of apppropriate statistical methodologic techniques for all analyses. Staff of the Core will continue to be active collaborators in publications from this research. It will be responsible for collaboration in the design of all forms used, will continue to improve and operate data entry/data management procedures to achieve the most cost-effective computer utilization for the present and proposed studies. Methodologic developments will be pursed in constructing multivariate models for the cross-sectional/longitudinal data which are an important focus of the Program Project.